One time disable
If at any time the driver/front passenger quickly buckles then unbuckles
the BeltMinder feature for that seating position, the BeltMinder is
disabled for the current ignition cycle. The BeltMinder feature will
re-enable during the same ignition cycle if the occupant buckles and
remains buckled for approximately 30 seconds. Confirmation is not given
for the one time disable.
Deactivating/activating the BeltMinder feature
The driver and front passenger BeltMinder are
deactivated/activated independently. When deactivating/activating
one seating position, do not buckle the other position as this will
terminate the process.
Read Steps 1 - 4 thoroughly before proceeding with the
deactivation/activation programming procedure.
The driver and front passenger BeltMinder features can be
deactivated/activated by performing the following procedure:
Before following the procedure, make sure that:
 The parking brake is set
 The gearshift is in P (Park) (automatic transmission)
 The ignition switch is in the OFF position
 The driver and front passenger safety belts are unbuckled
2005 F-150 (f12)
Owners Guide (post-2002-fmt)
USA (fus)
Seating and Safety Restraints
122
To reduce the risk of injury, do not deactivate/activate the Belt
Minder feature while driving the vehicle.
1. Turn the ignition switch to the RUN (or ON) position. (DO NOT
START THE ENGINE)
2. Wait until the safety belt warning light turns off. (Approximately 1
minute)
 Step 3 must be completed within 50 seconds after the safety belt
warning light turns off.
3. For the seating position being disabled, buckle then unbuckle the
safety belt 9 times, ending in the unbuckled state. (Step 3 must be
completed within 50 seconds after the safety belt warning light turns
off.)
 After Step 3, the restraint system warning light (airbag light) will be
turned on for three seconds.
4. Within 10 seconds of the light turning on, buckle then unbuckle the
safety belt.
 This will disable the BeltMinder feature for that seating position if it
is currently enabled. As confirmation, the restraint system warning
light will flash 4 times per second for 3 seconds.
 This will enable the BeltMinder feature for that seating position if it
is currently disabled. As confirmation, the restraint system warning
light will flash 4 times per second for 3 seconds, followed by 3
seconds with the light off, then followed by the restraint system
warning light flashing 4 times per second for 3 seconds again.

I downloaded the owners manual from the Ford web site in PDF format. I then searched the manual for the word 'chime'. This procedure is on pages 122-123 in my manual under the haeding 'Seating and Safety Restraints'.

It wear mine! It's usually the person sitting next to me that doesn't and I get sick of telling them to pit it on so the chime will go off. Won't be a problem anymore thanks the responses on how to fix it!

Here in WV you can get a ticket for the passenger not wearing a seatbelt, so I just wait for the chime to go off and tell the passenger that there's nothing I can do about it and they need to buckle the seatbelt...Looking out for safety and for my wallet.

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